JPS63157132A - Electrochromic display element - Google Patents

Abstract

PURPOSE:To suppress a time aging deterioration of a display characteristic by providing a reference pole of a specific constitution, and controlling a voltage applied between a display pole and an opposed pole, based on the potential of the display pole to the reference pole, as a reference. CONSTITUTION:A display pole 4 consisting of a transparent display electrode 2 and an electrochromic substance layer 3 is provided on a display side substrate 1 of light transmissivity, and an opposed pole 8 consisting of an opposed electrode 6 and a counter electrode substance layer 7 is provided on an opposed side substrate 5, and between both the poles 4, 8, an electrolyte 10 is enclosed. Also, for instance, on the inside surface of the substrate 5, a reference pole 11 consisting of an electrode layer 12 being independent from the pole 8, and a conductive polymer layer 13 is provided. In such a way, according to a three- terminal type structure, a voltage applied between both the poles 4, 8 can be controlled, based on the potential of the pole 4 to the pole 11 as a reference, by which a decrease of an effective applied voltage between both the poles 4, 8, which follows up deterioration, etc. of a layer 7 or a liquid 10 is corrected, and a time aging deterioration of a display characteristic can be reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention produces a predetermined pattern such as letters or patterns by causing an electrochromic material of a display electrode and a counter electrode material of a counter electrode to change color through an electrolytic solution. The present invention relates to an electrochromic display element that displays images.

[Conventional technology]

A typical example of this type of display element is a display electrode in which an electrochromic material layer is provided on the inner surface of a light-transmitting display-side substrate via a transparent display electrode, and the display electrode is divided into segments constituting a required pattern. It is known that a counter electrode material layer is provided on the inner surface of the opposing substrate via a counter electrode to serve as the opposing electrode, and an electrolytic solution is sealed between the two electrodes of the side substrate facing each other with a spacer interposed therebetween.

In such a display element, by applying a voltage to the display electrodes corresponding to the required segments using the above-mentioned counter electrode as a common electrode, color change of the reactant through the electrolyte between the electrochromic substance and the counter electrode substance is performed. , the required display is made on the surface of the display side substrate. For example, in the case of blue display, tungsten oxide (Woo+) is generally used as the electrocomic material, but the color change in this case occurs when a lithium salt dissolved in a non-aqueous solvent is used as the electrolyte. , is based on the following reaction.

By the way, the counter electrode material layer of the counter electrode is generally made of conductive particles that also serve as a counter electrode active material such as carbon powder, or a combination of conductive particles and W.
O3, F ez 041 ・3 WOz, MnQ
It is composed of a layer in which oxide-based counter electrode active material powders such as z, IrQ, , Mo0= are bound together with a binder, or a layer in which activated carbon fiber cloth is adhered with a conductive adhesive. . Further, as an electrolytic solution, a solution in which a lithium salt is dissolved in a non-aqueous solvent as described above is widely used (documents unknown).

[Problem that the invention seeks to solve]

However, in conventional display elements, due to long-term use, deterioration of the counter electrode material layer, potential changes, and increase in resistance due to deterioration of the electrolyte cannot be avoided. There is a problem that the effective voltage applied between the displays decreases and the display characteristics deteriorate significantly over time.Also, if the same display is maintained in a colored state for a long time, the degree of coloration of the display gradually decreases. There was a drawback that this could not be precisely corrected by external control operations.

This invention was made to solve the above-mentioned conventional problems, and can significantly improve the deterioration of display characteristics over time due to deterioration of the counter electrode material layer, potential changes, deterioration of the electrolyte, etc., and can be used for a long time. An object of the present invention is to provide an electrochromic display element that can precisely control the degree of coloration of the display to a constant value when displaying the same display.

[Means for solving problems]

As a result of intensive studies to achieve the above object, the inventors found that a three-terminal device structure was created by providing a reference electrode with a specific configuration independent of the display electrode and the counter electrode inside the device. Since this reference electrode is extremely stable in terms of potential and is resistant to deterioration, by controlling the voltage applied between the display electrode and the counter electrode based on the potential of the display electrode with respect to the reference electrode, the counter electrode material layer This compensates for the decrease in the effective applied voltage between the display electrode and the counter electrode due to deterioration of the display, potential changes, deterioration of the electrolyte, etc., making it possible to significantly improve the deterioration of display characteristics over time. The present inventors have discovered that an electrochromic display element can be used that can precisely control the degree of coloring of a display to a constant value, and have thus completed the present invention.

That is, in the present invention, a pair of substrates whose at least the display side is translucent are placed opposite each other, a display electrode is formed by providing an electrochromic material layer on the inner surface of the display side substrate via a display electrode, and the opposite substrate In an electrochromic display element, in which a counter electrode is formed by providing a counter electrode material layer on the inner surface of the substrate via a counter electrode, and an electrolyte is sealed between the two materials, the display electrode is provided on the inner surface of the display side or opposing substrate. and an electrochromic display element, characterized in that an independent electrode layer is formed with respect to the counter electrode, and a conductive polymer layer imparted with conductivity by ion doping is provided on the electrode layer to serve as a reference electrode. Pertains to.

[Structure and operation of the invention]

As described above, the display element of the present invention has a three-terminal structure including a reference electrode in which a conductive polymer layer imparted with conductivity by doping with ions is provided on an electrode layer independent of the display electrode and the counter electrode. Since this reference electrode is extremely stable in terms of potential and does not easily deteriorate, the display is controlled by the potential of the display electrode relative to the reference electrode.In other words, the voltage applied to the display electrode and the opposite electrode during coloring is applied to the display electrode relative to the reference electrode. By controlling the potential of the poles to be kept at a constant value,
Deterioration of display characteristics due to deterioration of the counter electrode material layer, potential change, deterioration of the electrolytic solution, etc. is greatly suppressed, making it possible to provide clear display over a long period of time.

The reason why the reference pole can be used as an element drive control index in this way is considered as follows. In other words, a counter electrode material consisting of conductive particles or a layer of conductive particles bound to an oxide counter electrode active material powder with a binder, or a layer of activated carbon fiber cloth adhered to a counter electrode with a conductive adhesive. In the layer, the reversible transfer of charges accompanying the decoloring reaction is achieved by the formation of an unstable electric double layer on the surface, that is, the charging and discharging action of a double layer capacitor, or by electrochemical reactions including irreversible reactions. Therefore, potential changes are likely to occur, and functional deterioration over time due to deterioration is unavoidable, resulting in a decrease in the effective voltage applied between the display electrode and the counter electrode, resulting in a decrease in the amount of electricity injected during coloring.

On the other hand, if a conductive polymer layer is used for the reference electrode,
Extremely stable doping with anions makes it possible to obtain a stable reference electrode with very little change in characteristics even after long-term use. Therefore, if the voltage applied between the display electrode and the counter electrode is controlled so as to keep the voltage of the display electrode with respect to the reference electrode constant during decoloring, the deterioration in display characteristics caused by the counter electrode material layer can be corrected and the voltage will last for a long time. Clear display becomes possible.

Furthermore, in the display element of the present invention, when the same display is performed for a long time, a decrease in the degree of coloring of the display can be detected as a decrease in the potential by measuring the potential of the reference electrode. By applying a voltage between the display electrode and the counter electrode so that the potential of the reference electrode is maintained constant, it becomes possible to precisely control the degree of coloring of the display to be constant.

As the polymer material used for the conductive polymer layer of such a reference electrode, various polymer materials that have the property of acquiring conductivity through ion doping, which are known as electrode materials for so-called polymer batteries, are used. It is possible. Specific examples include polyaniline, polythiophene,
Examples include polypyrrole, polyacetylene, polyparaphenylene, and among these, the first three are preferred, and polyaniline is particularly optimal.

As the ions to be doped into such polymeric substances, anions that are the same as or similar to the anion component of the electrolyte used in the display element are suitable; for example, Cl0
a-, BF4-, PF6-1CF3So,”, B
Examples include φ4 (φ is a phenyl group), and two or more types of these may be doped. Note that the doping amount of these anions may be set so that the potential difference with the electrochromic substance used for the display electrode is approximately O, depending on the type of electrochromic substance used for the display electrode.

Note that in order to dope the polymer substance with ions,
Ions may be present at a required concentration in the medium used to synthesize this polymeric substance by electrolytic polymerization or the like.

The reference electrode in this invention may be formed on the inner surface of either the display side substrate or the counter side substrate, and is separated from the display electrode and the counter electrode. The electrode may be provided independently from the counter electrode and electrically isolated from the counter electrode.

As a specific means for forming the reference electrode, a part of the electrode layer for the display electrode or the counter electrode formed in advance on one surface of the display side substrate or the counter side substrate is subjected to a photoresist etching process or the like to form the display electrode or the counter electrode. Either divide the electrode layer so that it is electrically independent, or pattern it when forming the electrode film using a thin film formation method such as vacuum evaporation, and divide it in the same way, leaving the required area of the divided electrode layer. After masking the surface of the electrode layer with an insulating material, this substrate is immersed in the polymer substance synthesis medium containing doping ions, and the exposed electrode layer portion is used as an electrode to form a polymer by electrolytic polymerization. An example of this method is to synthesize a substance and deposit a conductive polymer layer on the electrode surface, and then remove the mask. In addition, when forming the counter electrode by depositing metal foil, a small area of metal foil separated from this metal foil is deposited on a part of the counter substrate as an electrode layer of the reference electrode, and this electrode layer It is also possible to form a reference electrode by synthesizing a polymer material by electrolytic polymerization using the portion as an electrode in the same manner as described above. The electrochromic display element of the present invention is characterized in that the above-mentioned reference pole is provided on the inner surface of the display side substrate or the opposing side substrate, but the other structure of this element may be the same as that of conventional elements. . Hereinafter, an example of the electrochromic display element of the present invention including the other configurations described above,
This will be explained with reference to the drawings.

In FIG. 1, 1 is a transparent display side substrate, and this substrate 1
An electrocomic material layer 3 is provided on the inner surface of the display electrode 2 via a transparent display electrode 2 to form a display electrode 4 divided into segments constituting a required pattern. Reference numeral 5 denotes a counter substrate, and a counter electrode material layer 7 made of an activated carbon material is provided on the inner surface of the substrate 5 via a counter electrode 6 to form a counter electrode 8. The side substrates 1.5 are arranged to face each other with a spacer 9 made of synthetic resin or glass interposed therebetween, and an electrolytic solution 10 is placed inside them, that is, between the two electrodes 4.8.
is included.

A reference electrode 11 is provided on the inner surface of the opposing substrate 5 independently of the opposing electrode 8, and as shown in FIG. layer 12
A conductive polymer layer 13 is formed thereon.

Although a translucent material such as glass is generally used for the above-mentioned side substrates 1 and 5, the opposing substrate 5 may be non-transparent. Further, the display electrode 2 is made of indium-
It is made of a transparent conductive material such as tin composite oxide (hereinafter referred to as ITO), and is usually made of 1,000~ It will be formed to a thickness of about 3,000 people. Further, as the counter electrode 6 and the electrode layer 12, transparent conductive materials similar to those described above, noble metals such as gold and platinum, and alloys of these and other metals are used. In this case, the inner surface of the opposing substrate 5 is usually coated with a film of 1,000 to 3.0 by pressing or adhering the foil-like material.
It is formed to a thickness of about 00 people.

The electrochromic material layer 3 is made of tungsten oxide (W
O3) A thin film is formed on the display electrode 2 by the same thin film forming technique as described above to a thickness of usually about 3,000 to 10.000 mm.

The counter electrode material layer 7 is made of carbon powder such as carbon black or carbon powder and WO+, Fez Os' 3WO3, M
A layer up to a thickness of about 200 μm formed by applying a paint containing an oxide-based counter electrode active material powder such as n○20, IrO2, MOO3 and a binder onto the counter electrode 6 using a screen printing method, or A cloth made of activated carbon fiber with a thickness of about 100 to 500 μm is attached to the counter electrode 6 using a conductive adhesive.
It consists of a layer attached to the top.

The conductive polymer layer 13 is made of a polymeric substance imparted with conductivity by doping with ions as described above, and as described above, the electrolytic polymerization method is carried out in a medium containing doping ions using the electrode layer 12 as an electrode. It is formed by etc. This thickness is preferably about 5 to 50 μm.

As the electrolytic solution 10, L I C10a, L iB
F4, LiPFn, LiCFx 303, LiB
A solution of a lithium salt such as φ4 (φ is a phenyl group) in a nonaqueous solvent such as propylene carbonate, or a solution prepared by adding a small amount of water to this is used. In addition,
The lithium salt is the conductive polymer layer 13 of the reference electrode 11.
It is preferable that the ion be the same as the ion doped into the polymer material in , but it may be one that can ionize similar anions.

Further, 14 is an insulating layer for protecting the exposed portion of the display electrode 2, and 15 is a background material that hides the counter electrode 8 and the reference electrode 11 and uses its own color tone as the background of the display. It is composed of an electrolyte-impregnated sheet-like molded product in which the pigment to be expressed is bound with a binder such as polytetrafluoroethylene, or a gel body of pigment and electrolyte.

In the illustrated configuration, the reference electrode 11 is provided on the inner surface of the opposing substrate 5, but in the present invention, it may be provided on the inner surface of the display substrate 1 as described above.

〔Effect of the invention〕

The electrocomic display element according to the present invention has a three-terminal structure in which a reference electrode with a specific configuration is provided on the inner surface of the display side or opposite substrate, which is independent of the display electrode and the counter electrode. It is possible to control the voltage applied between the counter electrode and the same electrode based on the potential of the display electrode with respect to the reference electrode, and this control allows the voltage applied between the electrode and the counter electrode to be controlled based on the potential of the display electrode with respect to the reference electrode. The reduction in the effective applied voltage between the display electrode and the counter electrode is corrected, making it possible to extremely minimize the deterioration of display characteristics over time.Also, changes in the degree of coloration of the display during long-term identical display can be measured by measuring the potential of the reference electrode. There is an advantage in that it is possible to detect and precisely control the degree of coloring based on this detection so that the degree of coloration is constant.

〔Example〕

Hereinafter, this invention will be specifically explained based on examples.

Example 1, 1 A predetermined pattern of display electrodes made of I'TO with a thickness of 3,000 tm and a display electrode with a thickness of 5,000 tm deposited on one surface of the display side substrate made of transparent glass with a thickness of 5,000 tm. An electrochromic material layer having a square pattern with a side of Ion made of tungsten oxide of It was installed as a display pole.

On the other hand, after forming an electrode layer made of ITO with a thickness of 3,000 on the entire surface of the opposing substrate made of transparent glass with a thickness of 1.1 fl using a resistance heating evaporation method, including the edge of the substrate of this electrode layer. A portion (about 1,21 CII) was divided by photoresist etching treatment, and this divided portion was used as the electrode layer of the reference electrode, and the remaining part was used as the counter electrode. Then, the required area of the divided electrode layer (1,0 J ), and insulation mask processing was applied to the other parts.

Next, using the opposite substrate with the above mask as an electrode plate, 0.5 molar concentration of aniline and 0.5 molar concentration of H
(Immersed in an aqueous solution in which 104 was dissolved, potential scanning was performed at -0, 2 to +0, 9 V (saturated calomel electrode) and a scanning speed of 150 mV/sec, and the exposed electrode layer surface was covered with a thickness of 10
After forming an aniline oxidation polymer film doped with μm of Cl0a” ions, the mask was removed and a reference electrode was constructed with a conductive polymer layer on the divided electrode layer. Activated carbon fiber (trade name: KRAKTIIB #700 manufactured by Kuraray Chemical Co., Ltd.) is used as the counter electrode material.
) with a carbon paste adhesive (product name: Carbon Ink RP-10 manufactured by Tokuriki Institute) to a thickness of 500I1.
A counter electrode material layer of m was formed to serve as a counter electrode.

Next, the above-mentioned side substrate was placed in such a manner that the display electrode and the counter electrode faced each other, and a sheet-like molded product of a mixture of titanium dioxide pigment and polytetrafluoroethylene powder with a thickness of 0.3 nm was placed between the two electrodes. A background material of 1.0 mol/l was loaded into the periphery, and an annular spacer made of polyethylene terephthalate with a thickness of 0.8 fl was interposed on the periphery to face each other, and the material was tightly sealed with an epoxy adhesive. Concentration of Li
1.0 in propylene carbonate solution containing Cj204
An electrolytic solution prepared by adding % by weight of pure water was sealed. and,
Finally, lead terminals were attached to each lead portion of the display electrode, counter electrode, and reference electrode to produce an electrochromic display element as shown in FIGS. 1 and 2.

Comparative Example An electrochromic display element was produced in the same manner as in the example except that the reference electrode was not formed.

Regarding the display element of the above embodiment, the voltage of the display electrode with respect to the reference electrode is -1, Ov on the display side, between the display electrode and the counter electrode.
A rectangular wave alternating current voltage is applied for 0.5 seconds and 10.5 seconds, or 1 cycle/second, so that the erase side is +1.0■, and the coloring and coloring cycles are continuously driven. The amount of electricity was measured. On the other hand, for the display element of the above comparative example, the distance between the display electrode and the counter electrode is ±1.0■, 0
．． A rectangular wave alternating current voltage was applied for 5 seconds and 10.5 seconds and cycle driving was performed in the same manner to measure the amount of electricity injected. These results are shown in the table below.

From the results in the above table, it can be seen that the display element (Example) of the present invention in which a reference electrode is formed can reduce injection as the number of cycles increases by controlling the applied voltage in each cycle based on the potential of the display electrode with respect to the reference electrode. It can be seen that the decrease in the amount of electricity can be extremely minimized and excellent display characteristics can be maintained over a long period of time. In contrast, in a display element with a conventional configuration without a reference electrode (comparative example), the amount of injected electricity decreases significantly as the number of cycles increases, and it is clear that the display characteristics deteriorate with long-term use. .

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of an electrochromic display element according to the present invention, and FIG. 2 is a plan view of the display element as seen from the inner surface of an opposing substrate on which a reference pole is formed.

Claims (2)

[Claims] (1) A pair of substrates whose display side is translucent at least are disposed opposite each other, a display electrode is formed by providing an electrochromic material layer on the inner surface of the display side substrate via a display electrode, and the inner surface of the opposing substrate In an electrochromic display element, in which a counter electrode is formed by providing a counter electrode material layer with a counter electrode interposed therebetween, and an electrolyte is sealed between the two electrodes, the display electrode and the counter electrode are provided on the inner surface of the display side or the counter substrate. An electrochromic display element characterized in that an electrode layer is formed independent of the electrode, and a conductive polymer layer provided with conductivity by ion doping is provided on the electrode layer to serve as a reference electrode. (2) The electrochromic display element according to claim (1), wherein the conductive polymer layer comprises at least one polymer selected from polyaniline, polythiophene, and polypyrrole doped with anions.